1. Field of the Invention
The present invention pertains to the compression of individual electromagnetic pulses, and in particular to the compression of individual soliton pulses.
2. Description of the Related Art
Commonly assigned U.S. Pat. No. 4,719,429 issued to the inventor of the present invention describes a transmission line microwave generator for generating a particular type of pulse known as a "soliton". Solitons are a class of travelling waves of interest to the scientific community. A field of study has been devoted to Solitons since the last century, the study beginning with an observation of shallow ocean waves. The term "soliton" is taken from mathematics which describe a wave shape of a non-linear pulse. Solitons are described in the book entitled, Solitons In Action, edited by K. Longren and A. Scott. More particularly, the present invention is concerned with a particular type of soliton, that type which satisfies the Korteweg-deVries (K-dV) equation.
The aforementioned U.S. Pat. No. 4,719,429 taught several transmission line structures having non-linear transmission characteristics and pulse dispersion characteristics, both of which are essential for producing soliton pulses. Certain applications benefit from pulse compression. For example, communication transmission lines carrying pulses are limited in their speed of operation by pulse build-up. Pulse compression would alleviate pulse build-up, thus allowing faster transmission rates.
U.S. Pat. No. 2,869,004, developed prior to soliton pulse theory and the dispersion relations necessary therefor, teaches a pulse generating electrical circuit having sequentially arranged lumped circuits with increasingly reduced time constant values. Discrete components were used to determine the time constant in successive state, and is not suitable for generating very short pulses.
Other circuits have been disclosed for modifying pulses. For example, U.S. Pat. No. 3,177,433 teaches a multistage delay line using varietur diodes in the various stages, for pulse stretching. This invention employes a temporal change of time constant instead of a spatial change. U.S. Pat. No. 3,654,419 discloses a frequency modulator circuit with lumped LC circuit elements. U.S. Pat. No. 4,707,619 discloses a particular geometry of saturable inductors. U.S. Pat. No. 2,700,114 discloses an LC network which provides impedance matching. U.S. Pat. No. 3,644,747 discloses spark gaps for replacing the saturable inductors employed in U.S. Pat. No. 2,869,004.
While generally satisfactory for their intended purposes, these circuits are not suitable for use with soliton pulses and the teachings of the above-mentioned patents do not consider soliton pulses and the need for maintaining certain circuit properties such as non-linearity and pulse dispersion, which are necessary to preserve soliton properties such as those defined by the K-dV mathematical solution. Accordingly, the need exists for obtaining spatial compression of soliton pulses in a manner which preserves the unique soliton characteristics.